A commonly used method to track the position of a radio signal-emitting tracked device is to use the time difference of arrival (or, equivalently, the phase difference of arrival) at various receivers or receiver antennae at known locations to determine the position of the tracked device. By solving the non-linear equations that arise with such systems, the position of the tracked device can be determined. Because phase (θ) and time (t) are related by θ=ωt, where ω is a radio frequency scalar, they are equivalent systems and subsequent descriptions are denoted by time or time differences, as appropriate.